Add the macro QSORT, a convenient wrapper for qsort(3) that infers the
size of the array elements and supports the convention of initializing
empty arrays with a NULL pointer, which we use in some places.
Calling qsort(3) directly with a NULL pointer is undefined -- even with
an element count of zero -- and allows the compiler to optimize away any
following NULL checks. Using the macro avoids such surprises.
Add a semantic patch as well to demonstrate the macro's usage and to
automate the transformation of trivial cases.
Signed-off-by: Rene Scharfe <l.s.r@xxxxxx>
---
contrib/coccinelle/qsort.cocci | 19 +++++++++++++++++++
git-compat-util.h | 8 ++++++++
2 files changed, 27 insertions(+)
create mode 100644 contrib/coccinelle/qsort.cocci
diff --git a/contrib/coccinelle/qsort.cocci b/contrib/coccinelle/qsort.cocci
new file mode 100644
index 0000000..a094e7c
--- /dev/null
+++ b/contrib/coccinelle/qsort.cocci
@@ -0,0 +1,19 @@
+@@
+expression base, nmemb, compar;
+@@
+- qsort(base, nmemb, sizeof(*base), compar);
++ QSORT(base, nmemb, compar);
+
+@@
+expression base, nmemb, compar;
+@@
+- qsort(base, nmemb, sizeof(base[0]), compar);
++ QSORT(base, nmemb, compar);
+
+@@
+type T;
+T *base;
+expression nmemb, compar;
+@@
+- qsort(base, nmemb, sizeof(T), compar);
++ QSORT(base, nmemb, compar);
diff --git a/git-compat-util.h b/git-compat-util.h
index 8aab0c3..d7ed137 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -977,6 +977,14 @@ void git_qsort(void *base, size_t nmemb, size_t size,
#define qsort git_qsort
#endif
+#define QSORT(base, n, compar) sane_qsort((base), (n), sizeof(*(base)), compar)
+static void inline sane_qsort(void *base, size_t nmemb, size_t size,
+ int(*compar)(const void *, const void *))
+{
+ if (nmemb > 1)
+ qsort(base, nmemb, size, compar);
+}
+
#ifndef REG_STARTEND
#error "Git requires REG_STARTEND support. Compile with NO_REGEX=NeedsStartEnd"
#endif
--
2.10.0